Trace the MAC back to its source. Look for: - A link flapping on a upstream switch, causing spanning tree TCNs and Spanning Tree reconvergence. - A unidirectional link on an upstream switch causing the loop. - A hub or switch connected to a portfast enabled access port where this mac is learned. Shut this port down and see if this breaks the loop. Regards, Sweta ... View more

Yes, looks like you are hitting this bug (CSCsw18530) and why this IMAX power error popup on Cisco switch: After a PD (connected to one of our ports) is turned on, the hardware keeps on monitoring the current drawn by the PD so if the current drawn by a PD exceeds the pre-configured cutoff current (ICUT) for a limited time (TCUT) then the power controller will shut it down and informs the software about the fault. The software upon hearing about this fault, will print out the "IMAX error" message, remove the power and start a timer to start detecting the PD after the expiry of that timer. So if the device is continuously misbehaving (i.e. drawing more than ICUT current even after TCUT time) then we will keep on powering it up and then shutting it down. Please try to connect longer cable (<50) and let me know if it's fix this issue or not. Regards, Sweta ... View more

What platform and IOS you are using? Do you see any MALLOCFAIL messages in the logs? ... View more

Yes you can do it. This configuration will work. Similar thread: https://supportforums.cisco.com/thread/2096090 Regards, Sweta ... View more

Hi Manu, Please find the answers inline: Question 1: That means the QoS packet need not go to  the CPU at all, right? All Cisco Catalyst switches perform QoS in dedicated hardware ASICs and do not use their main CPUs to process any of the QoS configurations. Question 2: Does that mean that, whatever the egress queueing we do, that will be hardcoded into all the individual ports automatically as soon as I configure those commands? Or it is like fast Switching, where first few packets go to CPU and remaining will be switched in the interface itself? They will be hardcoded as soon as you apply them. Question 3: What does PFC exactly does in 6500 Engines. If the individual line cards has hardware queues, what additional capability does PFC offer in these switches? In 6500 switches, the heart of QoS functionality resides on the PFC. The buffering is done on the port asics but all the actual decisions are taken by PFC, that's why we call it PFC qos. Please find list of QoS processes performed on 6500: Input Scheduling—Done by port ASICs. Layer 2 only, with or without a Policy Feature Card (PFC). Classification—Done by Supervisor or by PFC via the access control list (ACL) engine. Layer 2 only, without a PFC; Layer 2 or Layer 3 with a PFC. Policing—Done by PFC via the Layer 3 forwarding engine. Layer 2 or Layer 3 with a PFC (required). Packet Re-write—Done by port ASICs. Layer 2 or Layer 3 based on classification done previously. Output Scheduling—Done by port ASICs. Layer 2 or Layer 3 based on classification done previously. Question 4:  In 3750 Switches, if I give the following commands in a Fast Ethernet port: srr-queue bandwidth share 1 70 25 5 srr-queue bandwidth shape  30  0  0  0 priority-queue out Consider I have mapped Voice traffic to the priority queue no.1. Does this means the Voice traffic gets dropped if it's more than 30 Mbps. Or the drop will happen only in case of congestion? When you enable “priority-queue out” on an interface, it turns queue 1 into priority queue, and scheduler does not take into account the queue’s weight for calculations. Priority Queue will ignore shaped mode settings as well. 100% of the bandwidth will be used by queue 1. Regards, Sweta ... View more

Hi Jerome, As stated by Dahua and Matthew, 'show policy-map interface' command is not supported on 3750 and 3560 switches, even though it is allowed to be typed in the CLI. You always have an option to do a sniffer capture to confirm if the traffic is getting marked or not or use "show mls qos interface x/y stat" to watch out for the packets. Regards, Sweta ... View more

Hi Changdong, Please find the answers inline: I find there are Queuing Model for Catalyst 29**, 35**, 37**, 45**, 65**, look like they are some standards, am i right? The values displayed under 'sh mls qos maps' are the default or rather you can say 'standard' values. These are the Cisco recommended ones . But if they don't suit your network requirements, you can tweak them as per your need. if I want to implement END-TO-END Catalyst QOS in a new Campus network, where should I begin,how should I consider, what is the most important part during implementing? And Are there some real cases, which can let me know how cool the QOS is .. First you need to understand if you expect to have congestion in your netwrok. If you have congestion, you will need to  find out the amount of traffic for each type and which traffic is lesser important than others and can be dropped. Try looking at below link for some sample examples to get a better understanding of qos.: http://www.cisco.com/en/US/products/hw/switches/ps5023/products_tech_note09186a0080883f9e.shtml#qds The last question, this document guide   version is 3.3,November 2005, Is there some update, and the latest  version.. I believe this document covers all the required topics and their explanations. You can rely on this for your need. Regards, Sweta ... View more

Hi, Unfortunately we cannot implement auto-qos for IP phones and soft-phones together on an edge port. If you don't want to trust the ingress traffic using trust statement, we are only left with the option of using MQC (class-maps). You can create class maps to classify the two types of traffic received followed by mapping them to different queues. Regards, Sweta ... View more

Hi Jason, The override suffix is not supported on 6500 but you can have an alternative configuration for that. Try configuring a policy map that matches the ingress traffic followed by using set command to configure the desired cos value. Sample config below: access-list 10 permit any Class Map match-all TEST   Match access-group  10 policy-map COS class TEST   set cos 5 Regards, Sweta ... View more

Hi Lewis, The smartport roles on CE500 are based on the type of devices to be connected to the switch ports. If you had Cisco IP phones role for a port on CE500, in that case you can use auto-qos feature on 2960 which suffice most of the times. Or if you are connecting to other switch and your traffic is coming premarked at the source, you can simply trust the marking (mls qos trust cos/dscp). If however you are planning to mark traffic on the switch, we will have to apply the service policy. -Sweta ... View more

Packets in queue with lower bandwidth guarantee are more likely to be dropped. so, queue 1 needs to have lower bandwidth to drop more packets. ... View more

Hi, Please find the answers below: I'm still a little confused about the min/max values and how to determine what to use. The min threshold identifies the queue size percentage at which the WRED dropping starts to be applied, while the max threshold identifies the queue size level at which tail drops occur. Since the values for queue 1 & 2 are the same, what then gives preference to queue 2 over queue 1? You need to consider bandwidth ratios for the queues. If bandwidth ratios were the same, then they would be treated the same.  If bandwidth ratios were different, scheduler will remove lesser number of packets from queue having lower bandwidth guarantee. Regards, Sweta ... View more

Hi Sanjeev, Request you to share the model of switches and routers which you are using in your network. -Sweta ... View more

Hi Adam, As far as I know, for existing platforms there are no plans to change the prevailing architecture. This again comes from the fact that the ASICs used in different platforms have been designed in different ways. This however may be a possibility for upcoming products. -Sweta ... View more

Hi Jonathan, Please find answers inline: On fa0/3 : I assume that I apply the same configuration that I put on fa0/1 right ? Since i wan't to prioritize the same traffic The configs on egress will not be same as ingress as we would be using output-queues on the egress. There are separate maps that govern as to which marking will take which queue in ingress and egress (dscp-input-q and dscp-output-q). Hence the commands to map marking to queues are different when it comes to ingress and egress. All four egress queues (on a 3750 switch) participate in the SRR unless the priority queue is enabled. Once we enable priority queue, it gets higest priority and remaining three queues continue using SRR. You can make sure that your FTP traffic gets mapped to the priority queue and is treated on priority.  This is supported only on egress using 'priority-queue out' interface level command. Second case, I have two switch with a trunk between switch 1 gi0/1 ----------------- gi0/2 Switch 2     |                                             | fa 0/1                                       fa 0/3    |                                              | Client1                                     Client2 Same scenario like the first one for the priority thing. On fa 0/1 and fa 0/3 : I see what I have to put for the ingress part, but not for the egress part on this interface ?On gi0/1 and gi0/2 : I see what I have to put for the egress part, but not for the ingress part ? If your traffic is coming premarked at the source, you can simply trust the marking (mls qos trust cos/dscp) on all four ports. If however you are planning to mark traffic on the switch, we will have to apply the service policy on fa0/1 and fa0/3 inbound and apply trust command on gi0/1 and gi0/2. For prioritizing traffic, make sure that the traffic gets priority on both switches. This can be done by enabling 'priority queue-out' on all four interfaces as discussed above and ensuring that the marking for FTP traffic is mapped to go out of the priority queue. Regards, Sweta ... View more